Effect of support of Co-Na-Mo catalysts on the direct conversion of CO2 to hydrocarbons

A review of catalytic hydrogenation of carbon dioxide: From waste to hydrocarbons

With the rapid development of industrial society and humankind’s prosperity, the growing demands of global energy, mainly based on the combustion of hydrocarbon fossil fuels, has become one of the most severe challenges all over the world. It is estimated that fossil fuel consumption continues to grow with an annual increase rate of 1.3%, which has seriously affected the natural environment through the emission of greenhouse gases, most notably carbon dioxide (CO₂). Given these recognized environmental concerns, it is imperative to develop clean technologies for converting captured CO₂ to high-valued chemicals, one of which is value-added hydrocarbons. In this article, environmental effects due to CO₂ emission are discussed and various routes for CO₂ hydrogenation to hydrocarbons including light olefins, fuel oils (gasoline and jet fuel), and aromatics are comprehensively elaborated. Our emphasis is on catalyst development. In addition, we present an outlook that summarizes the research challenges and opportunities associated with the hydrogenation of CO₂ to hydrocarbon products.

Modified fischer-tropsch synthesis: A review of highly selective catalysts for yielding olefins and higher hydrocarbons

Global warming, fossil fuel depletion, climate change, as well as a sudden increase in fuel price have motivated scientists to search for methods of storage and reduction of greenhouse gases, especially CO2. Therefore, the conversion of CO2 by hydrogenation into higher hydrocarbons through the modified Fischer–Tropsch Synthesis (FTS) has become an important topic of current research and will be discussed in this review. In this process, CO2 is converted into carbon monoxide by the reverse water-gas-shift reaction, which subsequently follows the regular FTS pathway for hydrocarbon formation. Generally, the nature of the catalyst is the main factor significantly influencing product selectivity and activity. Thus, a detailed discussion will focus on recent developments in Fe-based, Co-based, and bimetallic catalysts in this review. Moreover, the effects of adding promoters such as K, Na, or Mn on the performance of catalysts concerning the selectivity of olefins and higher hydrocarbons are assessed.

Uncovering the reaction mechanism behind CoO as active phase for CO2 hydrogenation

Transforming carbon dioxide into valuable chemicals and fuels, is a promising tool for environmental and industrial purposes. Here, we present catalysts comprising of cobalt (oxide) nanoparticles stabilized on various support oxides for hydrocarbon production from carbon dioxide. We demonstrate that the activity and selectivity can be tuned by selection of the support oxide and cobalt oxidation state. Modulated excitation (ME) diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reveals that cobalt oxide catalysts follows the hydrogen-assisted pathway, whereas metallic cobalt catalysts mainly follows the direct dissociation pathway. Contrary to the commonly considered metallic active phase of cobalt-based catalysts, cobalt oxide on titania support is the most active catalyst in this study and produces 11% C2+ hydrocarbons. The C2+ selectivity increases to 39% (yielding 104 mmol h-1 gcat-1 C2+ hydrocarbons) upon co-feeding CO and CO2 at a ratio of 1:2 at 250 °C and 20 bar, thus outperforming the majority of typical cobalt-based catalysts.

Effect of the Configuration of Copper Oxide-Ceria Catalysts in NO Reduction with CO: Superior Performance of a Copper-Ceria Solid Solution

Various copper-ceria-based composites have attracted attention as efficient catalysts for the reduction of NO with CO. In this comparative study, we have examined the catalytic potential of different configurations of copper oxide-ceria catalysts, including catalysts based on a copper-ceria solid solution, copper oxide particles supported on ceria, and ball-milled copper oxide-ceria. The structurally different interfaces between the constituents of these catalysts afforded very different catalytic performances. The solid solution catalyst outperformed the corresponding ceria-supported and ball-milled CuO-CeO₂ catalysts. The copper cations incorporated into the ceria lattice strongly improved the activity, N₂ selectivity, and water vapor tolerance compared to the other catalyst configurations. The experimental observations are supported by first-principles density functional theory (DFT) studies of the reaction pathway, which indicate that the incorporation of Cu cations into the ceria matrix lowers the energy required for activating the lattice oxygen, thereby enhancing the formation and healing of oxygen vacancies, and thus promoting NO reduction with CO.

Direct conversion of CO2 to a jet fuel over CoFe alloy catalysts

The direct conversion of carbon dioxide (CO₂) using green hydrogen is a sustainable approach to jet fuel production. However, achieving a high level of performance remains a formidable challenge due to the inertness of CO₂ and its low activity for subsequent C–C bond formation. In this study, we prepared a Na-modified CoFe alloy catalyst using layered double-hydroxide precursors that directly transforms CO₂ to a jet fuel composed of C₈–C₁₆ jet-fuel-range hydrocarbons with very high selectivity. At a temperature of 240°C and pressure of 3 MPa, the catalyst achieves an unprecedentedly high C₈–C₁₆ selectivity of 63.5% with 10.2% CO₂ conversion and a low combined selectivity of less than 22% toward undesired CO and CH₄. Spectroscopic and computational studies show that the promotion of the coupling reaction between the carbon species and inhibition of the undesired CO₂ methanation occur mainly due to the utilization of the CoFe alloy structure and addition of the Na promoter. This study provides a viable technique for the highly selective synthesis of eco-friendly and carbon-neutral jet fuel from CO₂.

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An alloy is developed for the direct CO₂ hydrogenation to jet-fuel-range hydrocarbons

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The selectivity of the hydrocarbons (63.5%) exceeds the theoretical maximum value

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The CoFe alloy is the active phase in the coupling reaction between surface carbons

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The CoFe alloy is a highly efficient catalyst in the presence of a sodium promoter

Recent Advances in the Mitigation of the Catalyst Deactivation of CO2 Hydrogenation to Light Olefins

The catalytic conversion of CO2 to value-added chemicals and fuels has been long regarded as a promising approach to the mitigation of CO2 emissions if green hydrogen is used. Light olefins, particularly ethylene and propylene, as building blocks for polymers and plastics, are currently produced primarily from CO2-generating fossil resources. The identification of highly efficient catalysts with selective pathways for light olefin production from CO2 is a high-reward goal, but it has serious technical challenges, such as low selectivity and catalyst deactivation. In this review, we first provide a brief summary of the two dominant reaction pathways (CO2-Fischer-Tropsch and MeOH-mediated pathways), mechanistic insights, and catalytic materials for CO2 hydrogenation to light olefins. Then, we list the main deactivation mechanisms caused by carbon deposition, water formation, phase transformation and metal sintering/agglomeration. Finally, we detail the recent progress on catalyst development for enhanced olefin yields and catalyst stability by the following catalyst functionalities: (1) the promoter effect, (2) the support effect, (3) the bifunctional composite catalyst effect, and (4) the structure effect. The main focus of this review is to provide a useful resource for researchers to correlate catalyst deactivation and the recent research effort on catalyst development for enhanced olefin yields and catalyst stability.

Pulsed Laser in Liquids Made Nanomaterials for Catalysis

Catalysis is essential to modern life and has a huge economic impact. The development of new catalysts critically depends on synthetic methods that enable the preparation of tailored nanomaterials. Pulsed laser in liquids synthesis can produce uniform, multicomponent, nonequilibrium nanomaterials with independently and precisely controlled properties, such as size, composition, morphology, defect density, and atomistic structure within the nanoparticle and at its surface. We cover the fundamentals, unique advantages, challenges, and experimental solutions of this powerful technique and review the state-of-the-art of laser-made electrocatalysts for water oxidation, oxygen reduction, hydrogen evolution, nitrogen reduction, carbon dioxide reduction, and organic oxidations, followed by laser-made nanomaterials for light-driven catalytic processes and heterogeneous catalysis of thermochemical processes. We also highlight laser-synthesized nanomaterials for which proposed catalytic applications exist. This review provides a practical guide to how the catalysis community can capitalize on pulsed laser in liquids synthesis to advance catalyst development, by leveraging the synergies of two fields of intensive research.

Novel Heterogeneous Catalysts for CO2 Hydrogenation to Liquid Fuels

Carbon dioxide (CO₂) hydrogenation to liquid fuels including gasoline, jet fuel, diesel, methanol, ethanol, and other higher alcohols via heterogeneous catalysis, using renewable energy, not only effectively alleviates environmental problems caused by massive CO₂ emissions, but also reduces our excessive dependence on fossil fuels. In this Outlook, we review the latest development in the design of novel and very promising heterogeneous catalysts for direct CO₂ hydrogenation to methanol, liquid hydrocarbons, and higher alcohols. Compared with methanol production, the synthesis of products with two or more carbons (C₂₊) faces greater challenges. Highly efficient synthesis of C₂₊ products from CO₂ hydrogenation can be achieved by a reaction coupling strategy that first converts CO₂ to carbon monoxide or methanol and then conducts a C-C coupling reaction over a bifunctional/multifunctional catalyst. Apart from the catalytic performance, unique catalyst design ideas, and structure-performance relationship, we also discuss current challenges in catalyst development and perspectives for industrial applications.

Shedding Light Onto the Nature of Iron Decorated Graphene and Graphite Oxide Nanohybrids for CO2 Conversion at Atmospheric Pressure

We report on the design and testing of new graphite and graphene oxide-based extended π-conjugated synthetic scaffolds for applications in sustainable chemistry transformations. Nanoparticle-functionalised carbonaceous catalysts for new Fischer Tropsch and Reverse GasWater Shift (RGWS) transformations were prepared: functional graphene oxides emerged from graphite powders via an adapted Hummer's method and subsequently impregnated with uniform-sized nanoparticles. Then the resulting nanomaterials were imaged by TEM, SEM, EDX, AFM and characterised by IR, XPS and Raman spectroscopies prior to incorporation of Pd(II) promoters and further microscopic and spectroscopic analysis. Newly synthesised 2D and 3D layered nanostructures incorporating carbon-supported iron oxide nanoparticulate pre-catalysts were tested, upon hydrogen reduction in situ, for the conversion of CO2 to CO as well as for the selective formation of CH4 and longer chain hydrocarbons. The reduction reaction was also carried out and the catalytic species isolated and fully characterised. The catalytic activity of a graphene oxide-supported iron oxide pre-catalyst converted CO2 into hydrocarbons at different temperatures (305, 335, 370 and 405 °C), and its activity compared well with that of the analogues supported on graphite oxide, the 3-dimensional material precursor to the graphene oxide. Investigation into the use of graphene oxide as a framework for catalysis showed that it has promising activity with respect to reverse gas water shift (RWGS) reaction of CO2 to CO, even at the low levels of catalyst used and under the rather mild conditions employed at atmospheric pressure. Whilst the γ-Fe2O3 decorated graphene oxide-based pre-catalyst displays fairly constant activity up to 405 °C, it was found by GC-MS analysis to be unstable with respect to decomposition at higher temperatures. The addition of palladium as a promoter increased the activity of the iron functionalised graphite oxide in the RWGS. The activity of graphene oxide supported catalysts was found to be enhanced with respect to that of iron-functionalised graphite oxide with, or without palladium as a promoter, and comparable to that of Fe@carbon nanotube-based systems tested under analogous conditions. These results display a significant step forward for the catalytic activity estimations for the iron functionalised and rapidly processable and scalable graphene oxide. The hereby investigated phenomena are of particular relevance for the understanding of the intimate surface morphologies and the potential role of non-covalent interactions in the iron oxide-graphene oxide networks, which could inform the design of nano-materials with performance in future sustainable catalysis applications.

CO2 Hydrogenation over Nanoceria-Supported Transition Metal Catalysts: Role of Ceria Morphology (Nanorods versus Nanocubes) and Active Phase Nature (Co versus Cu)

In this work we report on the combined impact of active phase nature (M: Co or Cu) and ceria nanoparticles support morphology (nanorods (NR) or nanocubes (NC)) on the physicochemical characteristics and CO2 hydrogenation performance of M/CeO2 composites at atmospheric pressure. It was found that CO2 conversion followed the order: Co/CeO2 > Cu/CeO2 > CeO2, independently of the support morphology. Co/CeO2 catalysts demonstrated the highest CO2 conversion (92% at 450 °C), accompanied by 93% CH4 selectivity. On the other hand, Cu/CeO2 samples were very selective for CO production, exhibiting 52% CO2 conversion and 95% CO selectivity at 380 °C. The results obtained in a wide range of H2:CO2 ratios (1-9) and temperatures (200-500 °C) are reaching in both cases the corresponding thermodynamic equilibrium conversions, revealing the superiority of Co- and Cu-based samples in methanation and reverse water-gas shift (rWGS) reactions, respectively. Moreover, samples supported on ceria nanocubes exhibited higher specific activity (µmol CO2·m-2·s-1) compared to samples of rod-like shape, disclosing the significant role of support morphology, besides that of metal nature (Co or Cu). Results are interpreted on the basis of different textural and redox properties of as-prepared samples in conjunction to the different impact of metal entity (Co or Cu) on CO2 hydrogenation process.

A Critical Look at Direct Catalytic Hydrogenation of Carbon Dioxide to Olefins

One of the main initiatives for fighting climate change is to use carbon dioxide as a resource instead of waste. In this respect, thermocatalytic carbon dioxide hydrogenation to high-added-value chemicals is a promising process. Among the products of this reaction (alcohols, alkanes, olefins, or aromatics), light olefins are interesting because they are building blocks for making polymers, as well as other important chemicals. Olefins are mainly produced from fossil fuel sources, but the increasing demand of plastics boosts the need to develop more sustainable synthetic routes. This review gives a critical overview of the most recent achievements in direct carbon dioxide hydrogenation to light olefins, which can take place through two competitive routes: the modified Fischer-Tropsch synthesis and methanol-mediated synthesis. Both routes are compared in terms of catalyst development, reaction performance, and reaction mechanisms. Furthermore, practical aspects of the commercialization of this reaction, such as renewable hydrogen production and carbon dioxide capture, compression, and transport, are discussed. It is concluded that, to date, the catalysts used in the carbon dioxide hydrogenation reaction give a wide product distribution, which reduces the specific selectivity to lower olefins. More efforts are needed to reach better control of the C/H surface ratio and interactions within the functionalities of the catalyst, as well as understanding the reaction mechanism and avoiding deactivation. Renewable H₂ production and carbon dioxide capture and transport technologies are being developed, although they are currently still too expensive for industrial application.

Metallic bionanocatalysts: potential applications as green catalysts and energy materials

Microbially generated or supported nanocatalysts have potential applications in green chemistry and environmental application. However, precious (and base) metals biorefined from wastes may be useful for making cheap, low-grade catalysts for clean energy production. The concept of bionanomaterials for energy applications is reviewed with respect to potential fuel cell applications, bio-catalytic upgrading of oils and manufacturing 'drop-in fuel' precursors. Cheap, effective biomaterials would facilitate progress towards dual development goals of sustainable consumption and production patterns and help to ensure access to affordable, reliable, sustainable and modern energy.

Carbon Dioxide Hydrogenation into Higher Hydrocarbons and Oxygenates: Thermodynamic and Kinetic Bounds and Progress with Heterogeneous and Homogeneous Catalysis

Under specific scenarios, the catalytic hydrogenation of CO₂ with renewable hydrogen is considered a suitable route for the chemical recycling of this environmentally harmful and chemically refractory molecule into added-value energy carriers and chemicals. The hydrogenation of CO₂ into C₁ products, such as methane and methanol, can be achieved with high selectivities towards the corresponding hydrogenation product. More challenging, however, is the selective production of high (C₂₊ ) hydrocarbons and oxygenates. These products are desired as energy vectors, owing to their higher volumetric energy density and compatibility with the current fuel infrastructure than C₁ compounds, and as entry platform chemicals for existing value chains. The major challenge is the optimal integration of catalytic functionalities for both reductive and chain-growth steps. This Minireview summarizes the progress achieved towards the hydrogenation of CO₂ to C₂₊ hydrocarbons and oxygenates, covering both solid and molecular catalysts and processes in the gas and liquid phases. Mechanistic aspects are discussed with emphasis on intrinsic kinetic limitations, in some cases inevitably linked to thermodynamic bounds through the concomitant reverse water-gas-shift reaction, which should be considered in the development of advanced catalysts and processes.

A review of the catalytic hydrogenation of carbon dioxide into value-added hydrocarbons

We review the indirect and direct routes for CO₂ hydrogenation to hydrocarbons and recent developments in catalyst design, performance and mechanism.